Dynamic rheological properties of wheat starch gels as affected by chemical modification and concentration

In this study, dynamic rheological properties of wheat starch gels in the linear viscoelastic region (LVE), as a function of starch concentration (8 and 12% w/w) and chemical modification (cross-linking and hydroxypropylation) were studied. The hydroxypropylated wheat starch (HPWS) gels in both concentrations had greater yield stress values at flow point (tau(f) = 48.3-166.4 Pa) compared to the native (NWS) and cross-linked (CLWS) wheat starches. In addition, all the loss-tangent values (tan delta(LVE)) were obtained in the range of 0.08-0.17, indicated predominantly elastic behavior of the starch gels. Unlike the NWS and CLWS samples which exhibited an intermediate behavior between a weak and an elastic gel (tan delta = 0.14-0.64), the HPWS samples relatively showed an elastic gel behavior (tan delta = 0.10-0.11), which was not influenced by the concentration. CLWS had higher pasting temperature (T-s = 61.8 degrees C), final viscosity (eta(star)(f) = 739.0 Pa.s), setback viscosity (SB = 646.8 Pa.s) and lower maximum viscosity (eta(star)(max) = 519.0 Pa.s) and breakdown viscosity (B = 426.8 Pa.s) than the others. The results suggest that the HPWS (in terms of viscoelastic properties) and CLWS (in terms of paste properties) have specific dynamic rheological properties which can be applied in different gel-like foods.